Polycycloolefin monomers, such as dicyclopentadienes, dihydrodicyclopentadienes, norbornenes, norbornadienes and other norbornene-type monomers are known to undergo ring-opening polymerization reactions in the presence of a metathesis catalyst to form high modulus, high impact strength polyunsaturated hydrocarbon polymers. For example, U.S. Pat. No. 4,400,340 describes the production of a poly(dicyclopentadiene) (PDCP) from metathesis catalyst ring-opening polymerization of dicyclopentadiene. Similarly, U.S. Pat. Nos. 4,568,660 and 4,689,380 describe metathesis catalyst ring-opening copolymerization of dicyclopentadiene with such norbornene-type monomers as 1,4,5,8-dimethano-1,4,4a,5,8,8a-hexahydronaphthalene (DMHN) and 1,4,5,8-dimethano-1,4,4a,5,8,8a-octahydronaphthalene (DMON); U.S. Pat. No. 4,703,098 describes copolymers prepared from ring-opening metathesis catalyst copolymerization of dicyclopentadiene with dicyclopentadiene oligomers such as tricyclopentadiene and higher oligomers; and U.S. Pat. No. 4,701,510 describes preparation by ring-opening metathesis catalysis of polymers of DMON and norbornene and copolymers and terpolymers of such monomers with other norbornene-type monomers such as dicyclopentadiene, tricyclopentadiene and higher dicyclopentadiene oligomers.
Such polymeric materials, however, due to the presence of significant amounts of carbon-carbon unsaturation can be subject to degradation of their physical properties such as tensile elongation, structural integrity, modulus and impact strength by olefin oxidation on exposure to light, heat and/or air over periods of time. Thus it has been proposed to incorporate into such polymers sterically hindered phenolic or amine antioxidant compounds such as 2,6-ditertiarybutyl-paracresol and N,N'-diphenyl-1,4-phenylene diamine as stabilizers to delay such olefin oxidation. See, for example, U.S. Pat. No. 4,507,453. Amine compounds are preferred for use as antioxidants as they have been found to afford much better protection than other compounds against the loss of physical properties by olefin oxidation. Unfortunately, however, the use of such amine compounds has been limited due to their tendency to "bleed" or migrate to the surface of the polymer thereby causing polymer discoloration and also staining of painted surfaces by further migration through the paint film.
It is an object of this invention, therefore, to provide an antioxidant stabilizing system for polymers formed from ring-opening metathesis catalyst polymerization of polycycloolefin monomers such as dicyclopentadienes, tricyclopentadienes (and higher oligomers of dicyclopentadiene), norbornenes, norbornadienes, DMON, DMHN and other norbornene-type monomers, and copolymers and terpolymers formed from ring-opening copolymerization of mixtures of such monomers which effectively delays degradation by olefin oxidation of such of the polymers physical properties as mentioned above. It is a further object of this invention to provide such an antioxidant stabilizing system which does not cause discoloration of such polymers when incorporated therein, and does not cause discoloration of any paint systems which have been applied to such polymers for aesthetic purposes.